The present invention relates to a gaseous discharge display panel of multi-layer construction comprising a transparent front sheet, a rear sheet and an intermediate sheet inserted between the front and rear sheets and having a number of elongated through holes for confining a number of discharge spaces, a number of anodes each arranged near one end of the respective through holes, a number of cathodes each being provided near the other end of the respective through holes and a number of fluorescent layers applied on walls confining the discharge spaces, whereby said sheets form a hermetically sealed envelope and an ionizable gas is contained in the envelope.
Such a gaseous discharge display panel has been disclosed in a specification of a copending U.S. Pat. application Ser. No. 491,634 filed on July 25, 1974, now U.S. Pat. No. 3,952,221. This gaseous discharge panel has several important advantages over the known gaseous discharge display panels described in specifications of U.S. Pat. Nos. 3,626,235, 3,631,530 and 3,743,879, i.e. since the discharge spaces and fluorescent layers extend in parallel with the display panel and discharge plasma is produced near the fluorescent layers, ultra-violet rays from the discharge plasma can excite strongly the fluorescent layers without being absorbed in the ionizable gas and thus the fluorescent layers emit light rays of high brightness. However after various experiments it has been found that this display panel has the following drawbacks. Since the cathodes provided in the discharge spaces face directly the fluorescent layers, the fluorescent layers may be easily blackend due to spattering of cathode materials. Therefore it is difficult to maintain high brightness of displayed images during the life time. Moreover in order to switch discharges in the sequential discharge spaces at a high rate scanning anodes are arranged between the intermediate and rear sheets so as to produce preliminary discharge between the scanning anodes and cathodes, but the light rays due to the preliminary discharges may be seen from the outside and thus the brightness of backgrounds of the displayed images is increased and the maximum contrast range is limited. Further the construction of the display panel is rather complicated and thus it is quite difficult to manufacture the display panel, particularly a large scale display panel. In order to display color images three adjacent elongated holes for confining discharge spaces must be arranged very close to each other, each one of these discharge spaces including a respective kind of three fluorescent materials for producing three primary colors. In such a color display panel mutual interferences between the respective primary colors may easily occur and thus the quality of the displayed color image might be deteriorated. This disadvantages will become more when the image dot density becomes high. It has been found experimentally that it is quite difficult to cement hermetically the front and intermediate sheets and thus the gas may flow between the adjacent discharge spaces.
In order to form a number of small holes in the intermediate sheet with a high density by mean of, for example etching process, the thickness of the intermediate sheet must be very thin and this causes further difficult to obtain the complete hermetic seal.